US3936746A - FM receiver having transmitting function - Google Patents

FM receiver having transmitting function Download PDF

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Publication number
US3936746A
US3936746A US05/486,314 US48631474A US3936746A US 3936746 A US3936746 A US 3936746A US 48631474 A US48631474 A US 48631474A US 3936746 A US3936746 A US 3936746A
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United States
Prior art keywords
signal
frequency
receiver
controlling means
switch
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Expired - Lifetime
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US05/486,314
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English (en)
Inventor
Osamu Irie
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Sony Corp
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Sony Corp
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Publication date
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Publication of US3936746A publication Critical patent/US3936746A/en
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/38—Transceivers, i.e. devices in which transmitter and receiver form a structural unit and in which at least one part is used for functions of transmitting and receiving
    • H04B1/40—Circuits
    • H04B1/403—Circuits using the same oscillator for generating both the transmitter frequency and the receiver local oscillator frequency
    • H04B1/408—Circuits using the same oscillator for generating both the transmitter frequency and the receiver local oscillator frequency the transmitter oscillator frequency being identical to the receiver local oscillator frequency

Definitions

  • This invention relates to an FM receiver and, in particular, to an FM receiver that has a signal transmission capability.
  • a leakage portion of the local oscillating signal generated by the receiver local oscillator may be radiated from the receiver antenna as a spurious wave.
  • this spurious wave radiation can be exploited for signal transmission by modulating the frequency of the local oscillator with an external signal.
  • the FM receiver can be used as an FM transmitter by modulating the local oscillator signal with an audio information signal.
  • FM receivers having automatic frequency control circuits are known.
  • AFC circuits control the frequency of the local oscillator and the FM receiver incorporating such circuits usually includes an AFC switch for the selective utilization of this feature.
  • AFC switch for the selective utilization of this feature.
  • One of these additional switches is used to change the FM receiver from a signal receiving mode to a signal transmitting mode and, of course, to the signal receiving mode.
  • the other additional switch is used to turn off the transmitted signal, as by preventing the local oscillator from being modulated by the audio signal to be transmitted.
  • a still further object of the present invention is to provide an FM receiver having a signal transmission capability wherein the number of manually operable selecting switches is significantly reduced in comparison with the number of switches heretofore used by the prior art devices.
  • Another object of this invention is to provide an FM receiver having a signal transmission capability that is of relatively simple circuit construction.
  • an FM receiver having a signal transmission capability including an FM signal receiving circuit including a local oscillator and an FM detector for receiving and demodulating an FM signal to derive an audio signal therefrom; a frequency controlling circuit coupled to the local oscillator and responsive to a control signal applied thereto for controlling the oscillating frequency of the local oscillator; a first switch for selectively supplying a portion of the signal produced by the FM detector or a signal to be transmitted by the FM receiver to the frequency controlling means as a control signal therefor; and a second switch for selectively turning the control signal on or off.
  • FIGURE illustrates a circuit diagram in partial block form and partial schematic form of an FM receiver in accordance with the present invention.
  • the FM receiver 1 of the present invention is seen to comprise an antenna 2, a conventional FM signal processing circuit including a radio frequency amplifier 3, a mixer 4, an intermediate frequency amplifier 5, a limiter 6 and an FM detector 7. Also shown is a frequency controlling circuit including a variable capacitance diode 10, a first manually operable selecting switch SW1, and a second manually operable selecting switch SW2. Still further, a source of audio signals 14 is depicted.
  • the conventional FM signal processing circuit is comprised of a series circuit adapted to demodulate the FM signals received at the antenna 2 to thereby derive an audio frequency information signal at an output terminal 8. Accordingly, as is well known, the radio frequency amplifier 3 is connected to the antenna 2 and includes an output terminal connected to the mixer 4.
  • the mixer is adapted to generate an intermediate frequency signal that is related to the received FM signal in accordance with a local oscillator signal that is supplied thereto by the local oscillator 9.
  • the output of the mixer 4 is coupled to the intermediate frequency amplifier 5 which, in turn, is connected by the limiter 6 to the FM detector 7.
  • the FM detector is conventional in nature and supplies the output terminal 8 with the derived audio frequency information signal.
  • the detected output signal obtained at the output terminal 8 is supplied through an audio frequency amplifier to a conventional sound transducer, such as a loud speaker system, to thus reproduce sound in response to the detected output signal.
  • the local oscillator 9 is a conventional variable frequency local oscillating circuit including a resonance circuit (not shown).
  • the variable capacitance diode 10, connected to the local oscillator 9, is preferably connected in parallel with the resonance circuit of the oscillator. It is recognized that a variable capacitance diode admits of a capacitative reactance that is a function of a control signal applied thereto. As the magnitude of the control signal varies, the capacitative reactance exhibited by the variable capitance diode also varies. Consequently, since this diode is connected to the resonance circuit of the local oscillator 9, it is appreciated that the effective reactance of the oscillator varies in response to the alteration of the capacitative reactance of the diode 10. In an alternative embodiment, the variable capacitance diode 10 is replaced by other conventional variable reactance elements.
  • variable capacitance diode 10 is coupled to the first manually operable switch SW1 via low-pass filter 11. Accordingly, a control signal that is supplied to the variable capacitance diode from the switch SW1 is subjected to a filtering operation by the low-pass filter which, preferably, is comprised of a series resistor 11a and a shunt capacitor 11b.
  • the switch SW1 is comprised of a contact b connected to the low-pass filter 11 and includes further contacts a and c.
  • a movable contact armature d is adapted to selectively connect the contact b with either contact a or contact c.
  • the movable armature d may comprise a slidable arm having a dimension that engages the contact b with only one of the contacts a or c in accordance with the position of the slidable arm.
  • the contact b is connected to a movable contact, such as a pivotal switch arm adapted to engage the contact a in a first position and the contact c in a second position.
  • a movable contact such as a pivotal switch arm adapted to engage the contact a in a first position and the contact c in a second position.
  • the contact c of the switch SW1 is connected to the FM detector 7 via a low-pass filter 12.
  • This filter is similar to the aforenoted filter 11 and comprises a series resistor 12a and a shunt capacitor 12b.
  • the contact a of the switch SW1 is connected to a terminal t.
  • This terminal is adapted to supply signals to be transmitted by the FM receiver, such as audio signals, or the like.
  • the terminal t comprises an output terminal of a magnetic tape recording/playback device 14. As illustrated, signals recorded on the magnetic tape 16 are reproduced by a reproducing head 15 and amplified by an audio signal amplifier 17. These amplified signals are then supplied to the output terminal t from which they are adapted to be applied to the switch SW1.
  • the audio signals supplied to the terminal t are derived from a microphone.
  • various other signal generating devices may be used to supply the terminal t with suitable signals to be transmitted by the FM receiver 1.
  • the second manually operable switch SW2 is substantially similar to the aforedescribed switch SW1 and includes a contact b connected in common to the contact b of the switch SW1 and to the low-pass filter 11.
  • the switch SW2 further includes another contact a adapted to be supplied with a reference potential, such as ground, and a further contact c.
  • the further contact c is adapted to be electrically isolated and is here illustrated as not being electrically connected to further apparatus.
  • a movable armature d is included in the switch SW2 to selectively connect the contact b with either the contact a or the contact c.
  • the illustrated embodiment of the switch SW2 can be replaced by other embodiments of switches such as those described hereinabove with respect to the switch SW1.
  • the movable armature d of the switch SW1 is operated so as to provide a signal transmission path between the fixed contacts a and b thereof.
  • the switch SW2 has been operated so as to be disposed in its illustrated state wherein the fixed contacts a and b are interconnected, it is apparent that any signal supplied to the terminal b of the switch SW1 will be coupled to the contact b of the switch SW2, through the movable armature d to the fixed contact a thereof and thence to ground.
  • the capacitive reactance of the diode 10 will now vary in accordance with the audio signals that are supplied thereto. Consequently, as the capacitive reactance of the diode varies, the oscillating frequency of the local oscillator 9 likewise varies. Thus, a frequency modulated local oscillating signal is produced by the local oscillator. A leakage portion of this frequency modulated signal will now be radiated from the antenna 2 as a spurious wave.
  • This transmitted FM signal can, of course, be received by another FM receiver in a conventional manner.
  • the illustrated FM receiver 1 will now operate in its conventional receiving mode. That is, signals that might be provided at the output terminal t are no longer transmitted to the variable capacitance diode 10 and the local oscillating frequency is no longer varied in accordance with such output signals. However, a portion of the detected signal provided at the output terminal 8 by the FM detector 7 will now be transmitted through the low-pass filter 12 to the fixed contact c of the switch SW1, and through the movable armature d to the fixed contact b.
  • the switch SW2 is operated so as to admit of the condition illustrated, then the movable armature d connects the fixed contacts a b thereof such that the signal appearing at the fixed contact b of the switch SW1 is now conducted to ground. That is, the portion of the detected output signal that is obtained from the FM detector 7 and that is to be used as a frequency controlling signal is here by-passed to ground. Accordingly, the well-known automatic frequency control of the FM receiver 1 is prevented.
  • the switch SW2 is operated such that movable armature d connects the fixed contacts b c thereof, then the control signal derived from the FM detector 7 and supplied through the low-pass filter 12 and switch SW1 is now enabled to be transmitted through the further low-pass filter 11 to the variable capacitance diode 10. Consequently, the capacitance of the variable capacitance diode is varied in accordance with this supplied control signal and AFC operation of the FM receiver is performed. Hence, the local oscillating frequency of the signal produced by the local oscillator 9 is here varied in accordance with the detected output signal provided by the FM detector 7.
  • the switch SW2 as described hereinabove is used to selectively control AFC operation and local transmission. That is, this switch is used both as an AFC on/off switch and a transmission on/off switch. Consequently, the FM receiver 1 can here be controlled in its receiving mode to operate with AFC and to operate in a signal transmitting mode by a number of switching devices which is reduced from that heretofore required by the prior art receivers. Nevertheless, while reducing the number of switches that must be present, an operator retains full control over the switching of AFC, the switching of a receiving mode or a transmitting mode of the FM receiver and a switching on or off of a signal to be transmitted. Thus, by reducing the number of switches from three to two while retaining the capability of selectively controlling three switchable functions, the limited space requirements of an FM receiver can be advantageously utilized and the cost of producing such an FM receiver having a signal transmission capability is significantly reduced.

Landscapes

  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Transmitters (AREA)
  • Transceivers (AREA)
  • Circuits Of Receivers In General (AREA)
  • Input Circuits Of Receivers And Coupling Of Receivers And Audio Equipment (AREA)
US05/486,314 1973-07-31 1974-07-08 FM receiver having transmitting function Expired - Lifetime US3936746A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP1973090492U JPS5345534Y2 (enrdf_load_stackoverflow) 1973-07-31 1973-07-31
JA48-90492[U] 1973-07-31

Publications (1)

Publication Number Publication Date
US3936746A true US3936746A (en) 1976-02-03

Family

ID=14000010

Family Applications (1)

Application Number Title Priority Date Filing Date
US05/486,314 Expired - Lifetime US3936746A (en) 1973-07-31 1974-07-08 FM receiver having transmitting function

Country Status (7)

Country Link
US (1) US3936746A (enrdf_load_stackoverflow)
JP (1) JPS5345534Y2 (enrdf_load_stackoverflow)
AU (1) AU476404B2 (enrdf_load_stackoverflow)
BR (1) BR7406166D0 (enrdf_load_stackoverflow)
DE (1) DE2436673A1 (enrdf_load_stackoverflow)
GB (1) GB1469419A (enrdf_load_stackoverflow)
NL (1) NL7409957A (enrdf_load_stackoverflow)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5513980A (en) * 1995-03-03 1996-05-07 Rasmussen; Clair L. Method and apparatus to override the child-resistant mechanism of disposable lighters

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4759078A (en) * 1986-11-14 1988-07-19 Rose Communication Systems, Inc. Coordinated local oscillator receiving system
US5109545A (en) * 1990-02-09 1992-04-28 Rose Communications, Inc. Proximal cable-less communication system with intentional signal path
US5101505A (en) * 1990-02-09 1992-03-31 Rose Communications, Inc. Method and apparatus for selective sideband signal correction in a proximal cable-less communication system

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2379395A (en) * 1944-05-05 1945-06-26 Hartford Nat Bank & Trust Co Fm transceiver
US2846572A (en) * 1956-04-23 1958-08-05 Collins Radio Co Frequency modulation transceiver with combined frequency control
US2972047A (en) * 1955-11-21 1961-02-14 Gen Dynamics Corp Transmitter-receiver
US2991353A (en) * 1959-03-03 1961-07-04 American Telephone & Telegraph Automatic frequency control for multitransmitter radio system
US3219931A (en) * 1962-12-31 1965-11-23 Raytheon Co Transceiver modulator-demodulator employing common elements
US3509462A (en) * 1966-07-20 1970-04-28 Gen Dynamics Corp Spurious-free phase-locked continuously tuned transceiver system

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2379395A (en) * 1944-05-05 1945-06-26 Hartford Nat Bank & Trust Co Fm transceiver
US2972047A (en) * 1955-11-21 1961-02-14 Gen Dynamics Corp Transmitter-receiver
US2846572A (en) * 1956-04-23 1958-08-05 Collins Radio Co Frequency modulation transceiver with combined frequency control
US2991353A (en) * 1959-03-03 1961-07-04 American Telephone & Telegraph Automatic frequency control for multitransmitter radio system
US3219931A (en) * 1962-12-31 1965-11-23 Raytheon Co Transceiver modulator-demodulator employing common elements
US3509462A (en) * 1966-07-20 1970-04-28 Gen Dynamics Corp Spurious-free phase-locked continuously tuned transceiver system

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5513980A (en) * 1995-03-03 1996-05-07 Rasmussen; Clair L. Method and apparatus to override the child-resistant mechanism of disposable lighters

Also Published As

Publication number Publication date
DE2436673A1 (de) 1975-02-20
AU476404B2 (en) 1976-09-16
JPS5037415U (enrdf_load_stackoverflow) 1975-04-18
AU7148374A (en) 1976-01-22
NL7409957A (nl) 1975-02-04
JPS5345534Y2 (enrdf_load_stackoverflow) 1978-10-31
GB1469419A (en) 1977-04-06
BR7406166D0 (pt) 1975-05-27

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